It was determined that there was a correlation between the precipitation pH levels and the predicted longevity of the roof panels. The higher the pH, the lower the acidity in the precipitation, thus a longer expected roof panel performance. The reverse is true for the lower pH levels.The average panel life expectancy for 14 sites was 139 years. The lowest pH was 4.36 with a life expectancy of 66 years; the highest pH was 5.37 with a life expectancy of 375 years. After eliminating the highest and lowest, average life expectancy is 125 years. This average life expectancy is more than twice the 60-year life expectancy required by LEED v4.
During the roof system component assessment performed at all sites, the following information concerning the fasteners, pipe flashings and flashings (gutter and downspouts, rakes, etc.) was revealed:
- All 14 roof areas totaled together equal 171,875 square feet of roof area.
- The total cost expected to replace these components at varying times (approximately 30 to 45 years) was $131,501, yielding an average cost of 90 cents per square foot. During a 60-year time period, this cost is 0.015 cents per square foot per year (90 cents per square foot total), which averages well under 10 percent of the cost of a total roof replacement anytime throughout this time period. Therefore, these roofs will have a complete service life exceeding 60 years with an average of 90 cents per square foot expected for component repairs during the 60-year expected timeframe.
- The base roof materials and associated sealants were tested extensively and determined to not need any replacement of remedial work during the 60-year period.
METAL ROOF DESIGN
The MCA Galvalume study verified what industry experts had predicted for years. The in-service metal roof panels and associated components will last at least 60 years with minimal component repair. However, it must be emphatically stated that these roofing materials must be used in applications that are appropriate for their configuration and detailing, as well as their structural capacity.
PHOTOS: METAL ROOF CONSULTANTS INC.